Oil exploration has been difficult in sensitive environments such as the North Slope of Alaska since current vehicles can damage and destroy those environments. For example, vehicles having separate wheels can cause deformation to the ground and gouging of the ground surface while being operated. It is highly desirable under certain environmentally sensitive conditions to have a tracked vehicle which causes the least deformation of the ground as possible. Such uses include operation across frozen tundra typical of the ANWR region of the North Slope of Alaska.
While wheeled vehicles typically have highly refined independent suspension systems, tracked vehicles have been limited to rigid, non-compliant suspension systems. This has been a necessity partly due to the driving track wheels being rigidly mounted to the power train. Because of this rigid mounting, the vehicle causes the ground to conform to the track system, rather than the other way around.
Most tracked vehicles are powered by mechanically driven track wheels which are prone to problems. Tracked wheels are not known to have independent suspensions. Although better than separate wheeled vehicles, traditional tracked wheels such as those found on tractors, military vehicles and the like, have been also known to damage and gouge a ground surface.
U.S. Pat. No. 5,533,587 issued to Dow et al. on Jul. 9, 1996 discloses an articulated tracked vehicle for agricultural harvesting which reduces damage to fields and can be driven on paved roads at reasonable speeds. The vehicle has front and rear elements, linked by an articulating joint which permits turning and rotation of one element with respect to the other. Each element is motivated by a pair of tracked power units which are hydraulically driven by a heavy duty differential between the units. Each power unit is rotatably mounted solely on a shaft sleeve of the differential and is free to oscillate vertically and independently to absorb irregularities in its path. Each unit includes an endless elastomeric track which has two rows of lugs on its inner surface. A novel drive mechanism engages these lugs to motivate the vehicle. A sealed transmission housing in each power unit protects key drive elements from environmental damage without interfering with operation of the unit. The transmission is centrally disposed within each power unit to provide further protection from damage.
U.S. Pat. Nos. 6,044,921 and 6,220,377 issued to Lansberry on Apr. 4, 2000 and on Apr. 24, 2001, respectively, describes a vehicle with a driving track assembly and a pair of secondary driving assemblies disposed on opposing lateral sides of the track. Each secondary driving structure includes a ground engaging wheel. The driving track assembly includes an endless ground engaging track that drives the vehicle. The flanking driving structures also engage the ground and are rotated to impart force to the vehicle. A steering device is operatively connected to the secondary driving assemblies so as to affect a vehicle steering operation, wherein the ground engaging driving structures are operated to turn said vehicle with respect to said vehicle driving direction. Preferably, the force imparted to the vehicle by one of said ground engaging driving structures is greater than the force imparted to the vehicle by the other of the ground engaging driving structures, thereby causing the vehicle to turn with respect to the vehicle driving direction.
The '377 includes a secondary driving and steering structure includes a ground engaging driving and steering structure that is preferably a ground engaging wheel wherein the steering device is operatively connected to the secondary driving and steering assemblies. Preferably, the steering device control is operable to transfer a substantial portion of the load support from the central driving track assembly during straight ahead movement onto the secondary driving and steering assemblies during turning movements.
The Lansberry patents relate to vehicles for use on a wide range of terrain, including uneven and/or steep terrain having a variety of soil conditions. They also describe use of DC magnet motors for driving and alternate version of the vehicle. The DC permanent magnet motors that have a transmission incorporated in the motor, has fewer than ten moving parts and the transmission portion ensures that sufficient torque is available for rugged terrain.
However, the prior art fails to provide a track system that conforms to the ground, rather than the other way around. What is needed is a vehicle having a track system including electrically controlled wheels so that when the vehicle is traveling on environmentally sensitive terrain the vehicle causes the least deformation of the ground as possible.